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Development of a Large-scale Biosolids Composting Facility in California

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The County Sanitation Districts of Los Angeles County (Districts) are responsible for wastewater treatment and solid waste management for over 5 million people in Southern California. The Districts operate 11 wastewater treatment plants, which generate approximately 550,000 wet tons of biosolids per year. For over sixty years the Districts have beneficially reused biosolids from its centralized solids processing facility, employing composting as the main management option for over 35 years. The Districts currently maintain a diverse biosolids management program, which includes composting, direct land application, cement kiln injection, lime stabilization, and landfill options.

Due to the dynamic landscape of biosolids management in Southern California, created by a combination of ever tightening regulations and local ordinances, the Districts are shifting focus from shorter-term contract operations to longer-range partnerships and District owned facilities. The cornerstone of this program will be a large-scale composting facility in California's heavily agricultural Central Valley.

In 1999, the Districts began discussions with Westlake Farms, third generation farmers in Kings County, California, regarding the acquisition of farmland and development of a composting facility. In 2001, the Districts and Westlake Farms executed agreements for the purchase of approximately 14,500 acres of farmland and the joint permitting of a 900,000 ton per year composting facility. Several years were spent preparing an Environmental Impact Report and determining operational parameters, after which a Conditional Use Permit was unanimously approved by Kings County. The Districts have acquired the necessary solid waste facility permit, are nearing completion on the air quality and water board permits, and are well into the design phase of the project.

The Westlake Farms Composting Facility will have the capacity to process up to 500,000 wet tons per year of biosolids, and up to 400,000 wet tons per year of bulking agent, into an exceptional quality compost product. A certain amount of the bulking agent will need to be agricultural waste, that would otherwise have been open burned, which could be up to 150,000 tons per year at full capacity. The remainder of the bulking agent can be green waste from local communities or from Los Angeles County. The composting technology employed will be aerated static piles, featuring the GORE Cover System.

This system is comprised of three distinct phases, active composting, maturation, and curing, and is able to meet very stringent air emission limitations, as well effectively control odors. This presentation will cover the partnership and agreements with Westlake Farms, environmental review and permitting processes, and current research and design challenges of the Westlake Farms Composting Facility.

Document Type: Research Article


Publication date: January 1, 2008

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